THERMAL DYNAMICS OF A DRUM DRYER

The thermal dynamics of a top-loading drum dryer is studied with a view of deriving the transfer function for the thermal process involved. The drum which initially operates at a steady state, is subjected to a step change in the steam pressure and the response of the temperature of the outer surface of the drum is recorded. The normalised time domain response of the temperature T is analysed using the least squares method to a non-linear function. The time domain response is also transformed into the frequency domain using Fourier transforms and the transfer function is derived.     

INDIRECT THERMAL DRYING OF LIGNITE: DESIGN ASPECTS OF A ROTARY DRYER

ABSTRACT

An investigation of the thermal drying of lignite has been carried out, by using an indirect heat pilot rotary drum. The process aims at the production of dry lignite and clean steam as part of a gasification procedure. Both flighted and bare drum modes have been employed. Temperature profiles along the dryer length, the amount of evaporation (moisture conversion) and the solids residence time distribution (RTD) were measured. A non-isothermal model was tested under three different regimes of solids flow. Model integration, by taking account of experimental amount of evaporation at dryer exit and temperature profiles along the dryer length, has been utilized in the validation of drying kinetics and heat transfer correlations. Model predictions compare satisfactorily with the operating data of an indirect heat industrial lignite dryer. Overall heat transfer coefficients of the pilot rotary dryer were found to agree well with those reported for direct heat dryers.     

DETERMINATION OF RESIDENCE TIME OF GRAINS IN DRUM DRYER

Abstract

On the basis of the theoretical analysts of the forces applied to grains and moving locus of grains in rotary drum dryer, residence time and contact heating time of grains in the dryer were calculated. The values of calculation conformed to the measured values. These results supplied reliable foundation in theory and practice for further studying and improving the dryer. They also provided designers with references to construct similar type of dryers.     

SIMULATION OF THERMAL AND DISINFESTATION CHARACTERISTICS OF A FORAGE DRYER

The thermal morality data for the cocoon stage of the insect Sitodiplosis mosellana (Gehin) were fitted to a normal distribution function and a probit viability equation was developed. The equation was included in a new tunnel dryer simulation program to compute the cumulative mortality of the insect during baled- forage drying. From the analysis it became clear that the temperature of dried forage remained at or above 60 C during drying and thus 99.99% kill of the insect was assured.     

EXPERIMENTAL STUDY ON DRYING OF CHILLI IN A COMBINED MICROWAVE-VACUUM-ROTARY DRUM DRYER

ABSTRACT

This paper presents new data on drying chilli in a microwave-vacuum-rotary drum dryer. This novel technique is designed to combine the advantages of vacuum drying and evenly dispersed microwave energy in a rotary drum. The drying kinetic and the specific energy consumption at particular product moisture content were measured experimentally. Moreover, the effect of pressure inside the chamber and the rotational speed of the drum were also determined.     

EXPERIMENTAL STUDY ON DRYING OF CHILLI IN A COMBINED MICROWAVE-VACUUM-ROTARY DRUM DRYER

This paper presents new data on drying chilli in a microwave-vacuum-rotary drum dryer. This novel technique is designed to combine the advantages of vacuum drying and evenly dispersed microwave energy in a rotary drum. The drying kinetic and the specific energy consumption at particular product moisture content were measured experimentally. Moreover, the effect of pressure inside the chamber and the rotational speed of the drum were also determined.     

SIMULATION OF THERMAL AND DISINFESTATION CHARACTERISTICS OF A FORAGE DRYER

The thermal morality data for the cocoon stage of the insect Sitodiplosis mosellana (Gehin) were fitted to a normal distribution function and a probit viability equation was developed. The equation was included in a new tunnel dryer simulation program to compute the cumulative mortality of the insect during baled- forage drying. From the analysis it became clear that the temperature of dried forage remained at or above 60 C during drying and thus 99.99% kill of the insect was assured.     

INDIRECT THERMAL DRYING OF LIGNITE: DESIGN ASPECTS OF A ROTARY DRYER

An investigation of the thermal drying of lignite has been carried out, by using an indirect heat pilot rotary drum. The process aims at the production of dry lignite and clean steam as part of a gasification procedure. Both flighted and bare drum modes have been employed. Temperature profiles along the dryer length, the amount of evaporation (moisture conversion) and the solids residence time distribution (RTD) were measured. A non-isothermal model was tested under three different regimes of solids flow. Model integration, by taking account of experimental amount of evaporation at dryer exit and temperature profiles along the dryer length, has been utilized in the validation of drying kinetics and heat transfer correlations. Model predictions compare satisfactorily with the operating data of an indirect heat industrial lignite dryer. Overall heat transfer coefficients of the pilot rotary dryer were found to agree well with those reported for direct heat dryers.     

MODELING AND OPTIMIZATION OF A DRYER

This study deals with the modeling and the search for the optimum production capacity of a tunnel-dryer of the Californian type. The model is obtained from the heat and mass transfer balances at two levels, the product (fruits) level and inside the tunnel itself. The optimum condition is given by the maximum production capacity of a plum dryer satisfying the final product quality. This choice is determined by the fact that a large amount of fruit must be dried in a short time to have a minimum of loss. Recirculation of a proportion of the exhaust air improves the dryer efficiently in terms of energy.     

金纳米线热稳定性的分子动力学模拟研究

采用三维分子动力学模拟方法,以面心立方金属金为研究对象,基于Finnis—Sinclair型嵌入原子法（EAM）多体势,模拟研究了金纳米线的热稳定性。研究表明,金纳米线的熔化温度随着线径的减小而降低,熔化过程从表面开始,并逐渐向中心趋近,最后缩聚成球形团簇。纳米线在熔化过程中,温度也在逐渐升高,这不同于块体材料。Au纳米线的熔点比块体材料低很多,并且与纳米线的线径倒数成线性关系。     

DRUM DRYING OF FABRICS

Abstract

A study of drying of textile fabrics on a drum heated by natural gas burner is presented. In the first stage of study, the distribution of the heat flux over the outer surface of the drum is calculated by an analytical method. In the second stage, this heat flux is entered in a numerical code able to simulate the heat and mass transfers in porous media. The simulation results validate the analytical model assumptions. Special attention is paid to the contact resistance between the drum and the fabric.     

有滞后环节的系统的闭环鲁棒辨识方法

提出一种新的针对带滞后环节的任意阶系统的闭环辨识方法。通过“三步法”,实现在闭环条件下的被控制对象的传递函数参数的辨识,所提出方法具有很强的鲁棒性。仿真例子表明该方法的有效性。     

H型气体水合物导热系数的分子动力学模拟

气体水合物^[1]是由水和小分子气体形成的非水学计量型笼型晶体。到目前为止,已经发现的气体水合物结构有3种,即Ⅰ型、Ⅱ型和H型,水合物的导热系数是一个很重要的物性参数,人们已对Ⅰ型和Ⅱ型水合物的导热系数进行了较多的实验和理论研究,包括分子模拟研究^[2],由于H型水合物发现较晚,其导热系数无论是实验值还是理论值均未见文献报道,因此本文对H型水合物的导热系数进行了分子动力学模拟。为了给H型气体水合物导热系数的模拟计算提供可靠的热能模型和模拟算法,本文首先对冰体系和空水合物的导热系数进行了分子动力学模拟。     

DRYING OF POWDERY MATERIALS IN A PULSED FLUID BED DRYER

ABSTRACT

Drying of recycled polypropylene powder was studied experimentally in a laboratory pulsed fluid bed dryer (PFB) with relocated air stream. It was proved that fluidization of fine particles having a large specific surface area and a broad size distribution is technically feasible when using the composite supporting grid. Drying and hydrodynamic characteristics for a pulsed fluid bed of fine particles are found to be similar to the ones for coarse particles. Equations for minimum pulsed fluidization velocity, pressure drop, and surface and volumetric heat transfer coefficients are given.     

EXPERIMENTAL INVESTIGATION OF FLOW PATTERN IN A SPRAY DRYER

1nvest.igation of flow pattern in a cocurrent disk spray dryer by means of measurement, of the kernel function is described. The obtained measurement results not only inform on the air flow type but ran be directly applied as input in the integral equation based simulation of heat and mass transfer.     

AN RTD STUDY FOR THE FLOW OF LIGNITE PARTICLES THROUGH A PILOT ROTARY DRYER PART I; BARE DRUM CASE

ABSTRACT

In Part I of the present work a pilot rotating cylindrical drum, without an internal lifting flight system (bare) has been employed for the study of lignite motion through it, at ambient temperature. Tracer pulse stimulus - response experiments have been carried out io deduce residence time distribution ( RTD) data and relate them to the operating conditions ( slope, speed of revolution, etc.). Mean residence time, space-time and solids hold-up have been correlated with the drum operating conditions. Experimental data of mean axial velocity of solids have been compared with theoretical predictions and found to deviate within a ± 15% margin. A size segregation of particles during their motion through the kiln under a variety of operating conditions has been confirmed and quantified. An average maximum divergence of 20% between the residence time of the smallest and that of the largest nominal particle sizes has been assessed.     

AN RTD STUDY FOR THE FLOW OF LIGNITE PARTICLES THROUGH A PILOT ROTARY DRYER PART II: FLIGHTED DRUM CASE

ABSTRACT

In Part II of this work a flighted pilot rotating cylindrical drum, intended to be used as either a dryer or calciner ( kiln) has been used to investigate the flow, through it, of pulverized moist lignite. Tracer pulse input - response experiments have been performed. Residence Time Distribution ( RT) data have been deduced for three types of flight geometry, namely: Rectangular ( RA) Equal Angular Distribution ( E.A.D.) and Equal Horizontal Distribution ( E.H.D) For each flight shape, mean residence time t¯ has been correlated with drum operating conditions. The sequence ? t¯ _EAD t¯ _EAD has been validated. A comparison between the residence time predictions for the flighted and the bare drum has indicated that t for the former may be higher by up to 3.5 times than that for the latter. Exceptionally high solids hold-up values ( Z= 0.13? 0.42) have been observed and compared to theoretical predictions. Particle size segregation during lignite flow through the flighted drum was not confirmed.     

AN RTD STUDY FOR THE FLOW OF LIGNITE PARTICLES THROUGH A PILOT ROTARY DRYER PART I; BARE DRUM CASE

In Part I of the present work a pilot rotating cylindrical drum, without an internal lifting flight system (bare) has been employed for the study of lignite motion through it, at ambient temperature. Tracer pulse stimulus - response experiments have been carried out io deduce residence time distribution ( RTD) data and relate them to the operating conditions ( slope, speed of revolution, etc.). Mean residence time, space-time and solids hold-up have been correlated with the drum operating conditions. Experimental data of mean axial velocity of solids have been compared with theoretical predictions and found to deviate within a ± 15% margin. A size segregation of particles during their motion through the kiln under a variety of operating conditions has been confirmed and quantified. An average maximum divergence of 20% between the residence time of the smallest and that of the largest nominal particle sizes has been assessed.     

EFFECT OF BLOW BOXES ON EVAPORATION DURING CYLINDER CONTACT IN A PAPER MACHINE DRYER SECTION

ABSTRACT

In this paper an inexpensive configuration for a cylinder blow box (CBB) and its effect on the evaporation rate are described. The objective of this work was to determine the effect of the blow boxes on drying intensity on a paper machine. The pilot machine trials were simulated with a computer program. Based on these results two cases were simulated for a commercial paper machine with and without blow boxes on single cylinders. The results revealed that when using the blow boxes on single cylinders, the drying rate can be increased by up to 15%. The potential for using this kind of configuration is biggest at the beginning of a dryer section. A simple construction of blow boxes makes this technique useful especially in boosting the drying performance of older paper and board machines. The exhaust air from the boxes can be utilized in ventilation of dryer pockets.